# std::layout_stride::mapping<Extents>::required_span_size

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< cpp‎ | container‎ | mdspan‎ | layout stride‎ | mapping

constexpr index_type required_span_size() const noexcept; |  | (since C++23)

Returns the required size of the mapping.

Let s be equal to:

- 1, if extents().rank() == 0 is true,
- otherwise, ​0​, if the size of the multidimensional index space extents() is ​0​,
- otherwise, 1 plus the sum of products of extents().extent(r) - 1 and extents_type::`index-cast`(strides_[r]) for all r in the range `[`​0​`,` extents().rank()`)`.

A call is equivalent to return s;.

### Return value

The required size of the mapping.

### Example

| This section is incomplete Reason: no example

### See also

required_span_size | returns the required size of the mapping (public member function of `std::layout_left::mapping<Extents>`)
required_span_size | returns the required size of the mapping (public member function of `std::layout_right::mapping<Extents>`)
size | returns the size of the multidimensional index space (public member function of `std::mdspan<T,Extents,LayoutPolicy,AccessorPolicy>`)

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